Transition metal nanoparticles: A missing link between early Earth and early life

我们提出这一建议的动机是观察到，在产生氢的热液喷口中自然发生的化学反应与厌氧自养生物中碳和能量代谢的核心反应具有明显的相似性，厌氧自养生物使用二氧化碳固定的乙酰-CoA途径，将早期地球化学与原始细菌和古生物中的代谢反应联系起来。在前一个资助期的实验中，我们已经证明了两种自然存在的过渡金属矿物，阿瓦鲁特(Ni3Fe)和磁铁矿(Fe3O4)，在穆尔海姆作为纳米颗粒催化剂合成，在杜塞尔多夫的小型实验室反应堆中，在100°C的水存在下，可以将24bar的H2和CO2(40：60)重复转化为甲酸盐(约100毫米)、醋酸盐(约100微米)和丙酮酸盐(约40微米)。这一高度特异的产物光谱包括从H2和CO2到丙酮酸的乙酰辅酶A途径的前三个自由中间体。虽然Ni3Fe和Fe3O4都可以完成10酶途径的催化作用，但氮对氨基酸的掺入被证明是更具挑战性的，要求我们探索替代的、更极端的条件。在这里，我们将研究高压和高温条件(高达380°C和800bar)以及机械力化学产生适当激活的氮物种的能力，以便将其并入氨基酸中，氨基酸是碱基的生化构建块。在证明过渡金属可以特异性地催化NAD+依赖于H2的还原为NADH之后，我们将探索它们取代基于黄素的电子分叉最古老和保守的功能的能力：低电势铁氧还蛋白的依赖于H2的还原。如果成功，我们的发现将在原始自养生物的生理和氢气产生热液喷口的自然发生的多相催化之间建立化学进化联系，揭示新陈代谢和生命如何出现的长期问题。

Motivation for our proposal is the observation that naturally occurring chemical reactions in H2 producing hydrothermal vents bear detectable similarity to the core reactions of carbon and energy metabolism in anaerobic autotrophs that use the acetyl-CoA pathway of CO2 fixation, linking early earth chemistry to the metabolic reactions in primitive bacteria and archaea. In experiments from the previous funding period we have shown that two naturally existing transition metal minerals, awaruite (Ni3Fe) and magnetite (Fe3O4), synthesized as nanoparticular catalysts in Mülheim, will reproducibly convert 24 bar of H2 and CO2 (40:60) to formate (ca. 100 mM), acetate (ca. 100 micrometers), and pyruvate (ca. 40 micrometers) overnight at 100°C in the presence of water in small laboratory reactors in Düsseldorf. This highly specific product spectrum comprises the first three free intermediates of the acetyl-CoA pathway from H2 and CO2 to pyruvate. Although Ni3Fe and Fe3O4 can both fulfill the catalytic role of the 10-enzyme pathway, nitrogen incorporation to amino acids has proven more challenging, requiring us to explore alternative, more extreme conditions. Here we will investigate the ability of high pressure and high temperature conditions (up to 380°C and 800 bar) as well as mechanochemistry to generate suitably activated nitrogen species for incorporation into amino acids, the biochemical building blocks of bases. Having shown that transition metals can specifically catalyze the H2 dependent reduction of NAD+ to NADH, we will explore their ability to replace the most ancient and conserved function of flavin based electron bifurcation: the H2 dependent reduction of low potential ferredoxin. If successful, our findings will forge chemical evolutionary connections between the physiology of primitive autotrophs and naturally occurring heterogeneous catalysis in H2 producing hydrothermal vents, shedding light on longstanding questions of how metabolism, and life, could have arisen.